BECE Past Questions & Answers – 1990 (SCIENCE)

SCIENCESectionB

SOLUTIONS

ESSAY

1. (a)

(i) Compound:
A substance formed bythe chemical combination ofelements in fixed proportions

Or: a substancecontainingtwo ormore elementsthat arechemicallycombined

(ii) Mixture
A physical combination of two ormoresubstances
Or:
A substance consistingof twoor moresubstancesthat havebeen combinedphysically

(iii) Element
A substancethat is madeup ofthe same kind of atoms
Or:
Anysubstancethat cannot be broken down into asimpleronebya chemical reaction

(iv) Solute
A substancethat is dissolved in anothersubstance

(b) Energy changes
(i) Amango drops fromatree.
Potential →Kinetic→Sound
(ii) A carpenterhits a nailwith a hammer.
Chemical→Potential →Kinetic→Sound +Heat
(iii) A torchis switchedon.
Chemical→Electrical →Light

(c) (i) A well-labeled diagramofaflower

(ii) Importanceof flower to plant
Sexual reproduction bysexcells
Seed development(ovuledevelops into seed)
Fruit production(ovarydevelops into fruit)
Attraction ofbirds and insects bypetals / nectar(for cross pollination)

(d) SENSEORGAN
Skin FUNCTION
Touch
Eye Sight
Nose Smell
Tongue Taste
Ear Hearing

2. (a) (i) Soilerosion
Thewashingawayof thetop soilbyagents of erosion
Or: The removal ofsoil material bynaturalprocesses,principallyrunning water, glaciers, waves, andwind

Types ofsoil erosion: Gully, Rill, Sheet and Splash [anytwo]

(ii) Activities ofmanthatcancausesoil erosion
 Removal of covercrops
 Bush burning
 Ploughing alongslopes
 Fellingof trees
 Sand-winning [anythree]

(iii) Ways by whichsoil canbe conserved
 Mulching
 Manuring

 PracticingCroprotation
 Plantingof cover crops
 Plantingmoretrees
 Practicingstripcropping

(b) (i) A lever
Simple machine consistingofa rigid barthatrotates about a fixed point, called apivot/
fulcrum

FIRST CLASS
SECONDCLASS
THIRD CLASS
A pair ofscissors
Clawhammer Bottle opener
Paper cutter Sugar tong fishingrod

(c) (i)Physical orchemical (ii) reversible orirreversible
(α) Some boiled cassavaandplantain werepounded together into fufu. (i) Physical (ii) irreversible

(β) A pieceof iceblock is put in a cup. Afterawhile,itis found out that theblock had changed into aliquid
(i) Physical (ii) reversible

(γ) A clean pieceof nailwasput into a beaker of water. Afterfivedays itwas observed that thecolourofthe nailhad changed
(i) chemical (ii) irreversible

3. (a)

DISEASE CAUSATIVE
ORGANISM
METHODOFPREVENTION

Cholera

bacteria
(Vibrio cholerae) Immunization /vaccination
Eatinghot meals
drinkingclean potablewater
washinghands with soapafter visitingthe toilet and beforemeals
coveringmeals to prevent flies from settlingon them
keepingour environment clean andfree from
filth
ensuringthat rubbish binsareproperlycovered

Bilharzia

flatworm
(blood fluke /schistosome) avoid touchingwaterbodies infected with the
vector (watersnails)
applychemicals to waterbodies infected with watersnails to kill thevector

Avoid pollutingwaterbodies

Malaria

Protozoon (plasmodium) Usingmosquito net
Usingmosquito repellent
Usinganti-malariadrugs
Clearingmosquito breeding grounds such as chokedgutters, stagnantpools of water,etc

Tuberculosis bacteria
(Mycobacterium tuberculosis) Immunization with BCGvaccine
Ensuring adequate ventilation
Avoid sharing cutlery, cups and glasses with infected persons [anyone for each]

(b) Howto separate themixtures: (i) Commonsalt andsand
I. Add waterto themixture and stir to dissolvethe salt
II. Pour the mixturethrougha filterpaper in a funnelto separate thesand (residue) from the saltsolution (filtrate)
III. Heat thesalt solution tillallthe waterevaporates,leavingthesalt crystals behind
IV. Drythe sand and thesalt obtained

(ii) Muddywater
 Fold a filterpaper into afunnel placed inabeaker.
 Pour themuddywaterthrough thefilterpaper in the funnel to separate thesuspended mud particles (residue)from thewater(filtrate)
 Thewater is collected inthe beaker, leavingthemud on the filterpaper.

(c) Why planets andtheir moonsmovearoundthesunwithout a clash
Each planetand each moon has a separate path (orbit) in whichit moves. Theyarekept in those separateorbits bythegravitational forces ofattraction between them and thelarger bodies
aroundwhich theymoveand hencedo not clash.

(d) Uses ofsun’s energy in everyday life
 Provision of light forseeing
 Dryingof clothes
 Preservation offoodbydrying
 Photosynthesisbygreenplants
 Electricitygeneration bysolar cells
 Synthesis of vitamin D bythe skin [anytwo]

4. (a) (i) Pollution
Contamination of Earth’senvironment with materials that interferewith human health,
the qualityof life, or thenatural functioningofecosystems

(ii)

TYPE OF POLLUTION POLLUTANT SOURCE

Air pollution

Smoke
carbonmonoxide

sulphurdioxide

Lead

Bush /tyreburning,
Motor-vehicle exhaust, Industrial processes
Sulphuric acid plants,
Power-generation facilities that useoilor coal containingsulphur
Motor-vehicle exhaust, batteryplants

Waterpollution

Sewage
 industrial wastes
 crudeoilspillage

Toxic chemicals
Homes, offices
Industries
Oil tankers, oil drilling rigs, oil refineries
Factories, Over-fertilized farmlands (through washing awaybyrain)

Land pollution Rubbish (non-
decomposable waste)

chemical fertilizers,

fungicides&pesticides Homes, offices,factories

Excessivefertilizer useby farmers
Indiscriminate application of fungicides and pesticides [anytwo types of pollution] [anyonepollutantand itssource for thetwo types]

(b) (i) Vegetativereproduction
Method bywhich plants reproducewithoutthe union of cells or nuclei of cells
Or:
Theprocess wherebyplants produceoffspring from growingparts / buds of theparent plant

(ii) Examples of plants that reproducevegetatively
Cassava, sugarcane,yam, cocoyam, banana, plantain, ginger, pineapple,etc

(c) (i) PART OFATOM ELECTRICALCHARGE
Proton +1
Neutron 0
Electron – 1

(ii) Work
Work is donewhen anapplied forcemoves an object in the direction oftheforce.
Or:
Thetransfer ofenergy, measuredas the product ofthe force applied to a bodyand the distancemoved bythat bodyin thedirection ofthe force
Or:
Work = f × d, where f = forceapplied
and d = distance moved in the directionoftheappliedforce

(iii)

HEAT TEMPERATURE
Theenergypossessed byabodythat
results in its hotness or coldness A measureof thehotnessor coldness
ofthe body

Unit = joule (J) Unit = kelvin (K) or
degeeCelsius (°C) or degreeFahrenheit(°F)